Study Of Multi-parameter Effects On Plasma-assisted Methane Pyrolysis And Oxidation

Plasma-assisted combustion,as a new technology for ignition and combustion enhancement,plays a very important role in rapidly heating gases,reducing ignition delay time,improving flame stability,broadening combustion limit,increasing flame propagation rate,and reducing pollutant emissions.Most of the researches on fuel combustion are currently concentrated on high-temperature ignition and combustion,comparatively,data of low temperature pyrolysis and oxidation are lacking.Low temperature pyrolysis and oxidation of fuels but plays a crucial role in the construction of the kinetic mechanism of methane combustion chemical reaction.So,exploration of low temperature kinetics for fuel combustion is necessary and pyrolysis and oxidation of methane fuel in the temperature range of 298-1173 K is accordingly conducted by experiments herein.In this paper,the experimental system for plasma-assisted fuel pyrolysis and oxidation are built.A parameterized high-voltage nanosecond pulsed power supply is used to excite the gas mixture.The main research contents and conclusions are as follows:(1)Experimental study of methane pyrolysis with different dilution gases Ar/He/N2Experimental results of methane pyrolysis with different dilution gases Ar/He/N2 show that the interaction mechanism between different dilution gas plasma with methane is different.Ar and He are easily ionized during discharge.The discharge power and the conversion rate of methane is higher,and the temperature of the discharge region is low.The dilution gas N2 system however has the highest discharge temperature and the methane conversion rate is comparatively lower.(2)Experimental study of nanosecond pulse discharge assisted methane pyrolysisEffects of pulse voltage,pulse repetition frequency,pulse width and other discharge parameters on the pyrolysis of CH4/He are studied.The inlet temperature of the mixture is controlled to explore the effect of nanosecond pulse discharge on the methane pyrolysis pathway.The results show as a result of pulse voltage and frequency increasing,the input of plasma energy and methane pyrolysis are significantly increased.The effect of pulse width is but opposite.The concentration of C2 and C3 hydrocarbon products increases first and then decreases with increasing temperature,and the concentration of H2 increases continuously.At high temperatures,fuel consumption increases dramatically,with a maximum conversion of methane of 80.72%.(3)Experimental study of nanosecond pulse discharge assisted methane oxidationEffects of pulse voltage,pulse repetition frequency,pulse width and other discharge parameters on the oxidation of CH4/O2/He are studied.The inlet temperature of the mixture is controlled to explore the effect of nanosecond pulse discharge on the methane oxidation pathway.The results show the addition of oxygen can generate a large amount of excited species such as O and OH,which significantly increases the consumption of methane.At low and medium temperature,the plasma plays a dominant role.At high temperature,some electron collision reactions are inhibited and the thermal effect is more competitive.The maximum conversion of methane is 82.49%.The product selectivity at different temperature is analyzed.